1. Field of the Invention
The present invention relates to a method of and an apparatus for production management for manufacturing products from semi-products and parts.
2. Description of the Related Art
On a product manufacturing or assembling line, parts are supplied to semi-products on the product manufacturing or assembling line to complete desired products. If the number of semi-products varies due to defective components thereof or a change in the production plan, then supplied parts become excessive or insufficient in number. If supplied parts become insufficient in number and a delay occurs in supplementing parts, then the efficiency with which final products are manufactured is lowered. If supplied parts become excessive in number, then it is necessary to retrieve those excessive parts and store them in a warehouse when the type of final products is to change.
Various processes have heretofore been proposed for the purpose of supplying parts efficiently to production lines. For example, an MRP (Material Requirement Planning) process employs a computer for establishing a production plan beforehand, and supplies the number of parts required to produce a predetermined number of products at times when those products are produced. Another process is known as a parts-on-demand process which supplies parts depending on how the production on a production line progresses, so that a constant number of parts are kept on the production line at all times.
Japanese laid-open patent publication No. 4-125205 discloses an automatic warehouse control system which determines the number of parts to be delivered from a warehouse based on data of parts delivered at a given time from the warehouse according to a production plan and the actual number of parts delivered from the warehouse as entered from a terminal, so that parts can stably be supplied even when the production of parts is changed or modified from the production plan. Since the disclosed automatic warehouse control system requires the operator to enter the actual number of parts delivered from the warehouse through the terminal, however, the entered data are not highly reliable, and it is not possible to compare, on a real-time basis, the actual number of parts delivered from the warehouse and the number of parts delivered according to the production plan. Consequently, the automatic warehouse control system is unable to manage the delivery of parts so as not to cause an excess or shortage of parts when the operation of a production line is to be finished.
A parts delivery system disclosed in Japanese laid-open patent publication No. 2-131829 operates to supply parts in synchronism with an assembly line even when a production plan changes or a disagreement occurs between a production plan and an actual production achievement. Specifically, the disclosed parts delivery system reads assembly progress information with respect to products being assembled from bar code data, compares the read assembly progress information with progress data according to a production plan, calculates the type, number, and delivery timing of necessary parts, and instructs a warehouse to deliver the parts and also instructs a conveyor system to convey the parts. The parts delivery system is capable of supplying parts in synchronism with the assembly line to a certain extent. However, because parts are supplied prior to their being assembled on the assembly line, if the number of products that are actually produced varies due to defective products or a failure of the assembly line after the parts are supplied, then the parts are supplied out of synchronism with the assembly line, resulting in an excess or shortage of parts.
Furthermore, the parts delivery system requires complex data processing by a computer, such as processing of bar code data and data comparison. As a consequence, the parts delivery system is too expensive and not practical for the application to a small-scale production line for assembling one part on one semi-product, for example.
It is a general object of the present invention to provide a method of and an apparatus for production management which does not bring about an excess or shortage of parts and hence does not require parts to be retrieved when a production process is finished, allowing a production line to be operated efficiently, and which is of a highly simple arrangement.
A major object of the present invention is to provide a method of and an apparatus for production management to supply a number of parts corresponding to a number of products smaller than a planned number of products to semi-products for thereby producing the products, counting a remaining number of any semi-products when all the parts are supplied to the semi-products, and supplying a number of parts corresponding to the counted number of semi-products to the semi-products for thereby producing the products, so that the products can be produced of the semi-products and the parts without causing an excess of parts.
The above and other objects, features and advantages of the present invention will become more apparent from the following description when taken in conjunction with the accompanying drawings in which a preferred embodiments of the present invention is shown by way of illustrative example.